This invention is directed to aircraft and more particularly to fairings suitable for use between two aerodynamic surfaces of an aircraft.
The present invention was developed for use, as will be better understood from the following description; as a fairing located between an engine nacelle and a leading edge flap. However, it will be appreciated, and should be understood, that the invention can also be utilized in other environments where two aerodynamic surfaces join and a fairing is required.
Many multiple engine aircraft are designed such that an interface exists between the nacelles of the aircraft engines and its wings. In addition, many such aircraft have leading edge wing flaps that are usually withdrawn when the aircraft is cruising and extended during takeoff and landing (and under other lower speed operating conditions). One example of an aircraft wherein such an interface exists is an upper surface blowing aircraft. In an upper surface blowing aircraft, jet engines are located above and slightly forward of the wings of the aircraft. The engines and the structure supporting them are surrounded by nacelles that interface with the leading edge of their associated wings. During normal flight, the exhaust stream is directed rearwardly to generate forward thrust in a conventional manner. Upon landing and takeoff, trailing edge flaps are employed with such aircraft to increase the camber and chord of the wing and at the same time to form a continuously curved, downward and rearward extension of the upper airfoil surface of the wing. When the trailing edge flaps are so extended, the exhaust stream traveling chordwise over the upper airfoil surface of the wing attaches itself by the Coanda effect to the downwardly and rearwardly curved surface to divert the exhaust stream downwardly and rearwardly. In this manner, a lift component, as well as a forward thrust component, is generated by the exhaust stream. The engine-generated lift component augments the conventional aerodynamic lift created by ambient air flow over the remaining portion of the wing to provide a STOL capability.
In addition to trailing edge flaps, upper surface blowing aircraft also include leading edge flaps that are extended to create a wing curvature that has high lift under low speed operating conditions, e.g., during takeoff and landing. The problem solved by the present invention relates to the interface between the leading edge flaps and the engine nacelles. Specifically, the curvatures of the engine nacelle and the leading edge flaps are such that it is difficult to maintain an acceptable aerodynamic surface where they interface. Often, because of this difficulty a gap exists between the leading edge flaps and the engine nacelle when the flaps are extended. This gap, because it is nonaerodynamic, results in poor flap performance and excessive drag.
In the past, in order to avoid poor flap performance and excessive drag, the gap between a leading edge flap and an engine nacelle has been filled in either of two ways. One way has been to fill the gap with a fairly large fixed fairing. The problem with this approach is that a large fixed fairing creates a drag penalty. The drag penalty exists not only when the flaps are extended, but also when the flaps are retracted, e.g., during cruise. Thus, while this approach overcomes some of the disadvantages of an unfaired interface, problems remain.
The second approach to filling the gap between an engine nacelle and a leading edge flap when the leading edge flap is extended has been to use an inflatable fairing. The problem with inflatable fairings is that their life is usually short and their maintenance cost is high. Thus, while solving the problem, inflatable fairings also have disadvantages.
Therefore, it is an object of this invention to provide an aerodynamic fairing suitable for use between two aerodynamic surfaces.
It is also an object of this invention to provide an aerodynamic fairing suitable for use between two aerodynamic members or surfaces that creates a minimal increase in frontal area, and therefore, creates a minimal increase in aircraft drag.
It is another object of this invention to provide an extendable aerodynamic fairing suitable for use between two aerodynamic members or surfaces.
It is a further object of this invention to provide an extendable aerodynamic fairing suitable for use between an aircraft engine nacelle and a leading edge flap.
It is yet another object of this invention to provide aerodynamic fairings suitable for use between the engine nacelles and the leading edge flaps of an upper surface blowing aircraft.